The present invention relates to a method for manufacturing a tire whose sidewall portion is provided with a projecting marking and a pneumatic tire manufactured thereby, more particularly to a structure of a tire vulcanizing mold comprising a stencil plate for forming a projecting marking.
Usually, as shown in FIG. 6(A), a tire T is provided in the outer surface of its sidewall portion Ts with a marking (e) which may be a character, diagram, symbol or the like.
Such marking (e) is usually molded by the use of a stencil plate interchangeably attached to the sidewall molding surface of a tire vulcanization mold. (cf. Japanese Utility Model application publication No. JP-U-H04-126838) more specifically, as shown in FIG. 6(B), the stencil plate (c) is placed in a recess (b) formed in the sidewall molding surface (a1) of the vulcanization mold (a) and having a depth substantially equal to the thickness of the stencil plate (c). The surface of the stencil plate (c) is provided with a marking part (c1) corresponding to the reverse of the marking (e) and protruding from the surface.    Thus, the marking (e) as a dent in the outer surface of the sidewall portion Ts is formed by the marking part (c1) during vulcanization. Incidentally, in FIGS. 6(A) and 6(B), such marking (e) and marking part (c1) are illustrated as having a circular form for the sake of simplicity.
In the meantime, when it is required to form a marking (e) as a protrusion from the outer surface of the sidewall portion Ts of a tire, the marking part (c1) in the surface of the stencil plate (c) has to be formed as a dent, for example, by the technique of engraving.
In the technique of engraving, however, there is a problem with long production time and high production cost.
Therefore, the present inventors proposed to use a thin metal plate as the stencil plate, and to form a marking part as a dent by the technique of press working from the front surface side of the plate.
In this technique, the production time and production cost for forming the concave marking part is remarkably reduced, and a concave marking part having a depth more than the thickness of the stencil plate can be formed without difficulty.
When the technique of press working is employed on the thin stencil plate (c), as shown in FIG. 7(A), a swollen part (f) is formed on the reverse side of the stencil plate (c). As a result, when such stencil plate (c) is placed in the recess (b), the stencil plate (c) is liable to becomes unstable and dislocated during vulcanization as shown in FIG. 7(B). Therefore, a gap (g) is formed between the stencil plate (c) and the vulcanization mold (a), and the rubber which penetrates into such gap (g), causes fins on the surface of the vulcanized sidewall portion. Thus, there is another problem of defective moldings.